Topical anti-inflammatory compositions comprising O/W emulsions containing pro-penetrating glycols

ABSTRACT

Topically applicable compositions in the form of oil-in-water (O/W) emulsions contain a pro-penetrating system including at least one glycol and at least one additional pro-penetrating agent, a suitable emulsifying system and at least one active agent of the family of steroidal anti-inflammatory agents, and are useful e.g., for the treatment of psoriasis.

CROSS-REFERENCE TO EARLIER APPLICATIONS

This application is a continuation of PCT/FR2007/050925, filed Mar. 14, 2007 and designating the United States (published in the French language on Sep. 20, 2007 as WO 2007/104895 A1; the title and abstract were also published in English), which claims priority under 35 U.S.C. §119 of FR060283, filed Mar. 15, 2006, each hereby expressly incorporated by reference in its entirety and each assigned to the assignee hereof.

CROSS-REFERENCE TO COMPANION APPLICATION

Copending U.S. patent application Ser. No. 12/232,305, filed concurrently herewith, now allowed, hereby expressly incorporated by reference and assigned to the assignee hereof.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to novel compositions in the form of an emulsion of oil-in-water (O/W) type for topical application, comprising a novel combination of pro-penetrating agents including at least one glycol, a suitable emulsifying system and an active agent of the family of steroidal anti-inflammatory agents.

2. Description of Background And/Or Related And/Or Prior Art

There currently exist many topical compositions comprising a steroidal anti-inflammatory agent and a high content of glycol, the latter promoting the penetration of the steroidal anti-inflammatory agent into the skin. Given the high content of pro-penetrating glycol, these compositions are formulated in the form of emulsions with a high content of fatty phase, which are also commonly known as “lipocreams”, in the form of anhydrous compositions known as “ointments”, in the form of fluid compositions with a high content of volatile solvents, such as ethanol or isopropanol, useful for application to the scalp, also known as “hair lotions”, or in the form of viscous O/W emulsions, which are also known as “O/W creams”.

For example, O/W creams comprising a corticoid and a high percentage of propylene glycol, marketed under the trademark Temovate® by Glaxo, are known. However, the stabilization of a formulation comprising such a percentage of glycol makes it necessary to include in the emulsion emulsifiers and stabilizers of glyceryl stearate or PEG 100 stearate type or, alternatively, stabilizers or consistency factors of white wax or cetostearyl alcohol type, which promote the formation of a thick cream of waxy appearance.

In FR 2 753 626, assigned to the assignee hereof, more fluid emulsions containing a corticoid that have a high percentage of propylene glycol. However, since the high percentage of propylene glycol makes it difficult to prepare the emulsion, it is advantageous to have available a novel stable formulation of O/W emulsion type, containing less propylene glycol, which has a non-greasy and non-tacky aspect, while at the same time maintaining the rheological and pro-penetrating properties of the composition.

SUMMARY OF THE INVENTION

The present invention thus features novel pharmaceutical compositions in the form of an emulsion of oil-in-water (O/W) type for topical application, comprising, formulated into a pharmaceutically acceptable vehicle:

a. at least one steroidal anti-inflammatory agent;

b. a pro-penetrating system which comprises at least one glycol and at least one additional pro-penetrating agent; and

c. a polymeric emulsifying system.

DETAILED DESCRIPTION OF BEST MODE AND SPECIFIC/PREFERRED EMBODIMENTS OF THE INVENTION

Among the steroidal anti-inflammatory agents that are exemplary, albeit non-limiting, are hydrocortisone, anthranoids, betamethasone valerate and clobetasol propionate. The steroidal anti-inflammatory agent is preferably clobetasol propionate.

Advantageously, the compositions according to the invention comprise from 0.0001% to 5% by weight and preferably from 0.025% to 1% by weight of an active agent relative to the total weight of the composition.

In one preferred embodiment according to the invention, the compositions comprise from 0.025% to 0.5% by weight and preferentially 0.05% by weight of clobetasol propionate relative to the total weight of the composition.

The principal advantage of the compositions according to the invention is to reduce the percentage of propylene glycol employed in the prior art by replacing the latter with a mixture selected such as to provide the desired pro-penetrating properties without encountering the previous difficulties of emulsification and of stabilization of the emulsion caused by the high percentage of propylene glycol.

Thus, the pro-penetrating system according to the invention comprises at least one glycol and at least one additional pro-penetrating agent.

The glycols employed according to the invention are:

-   -   alkylene or polyalkylene glycols. Non-limiting examples include         (C1 to C6) alkylene and polyalkylene glycols, such as ethylene         glycol, polyethylene glycol (2 to 20 monomers), propylene         glycol, dipropylene glycol, butylene glycol, pentylene glycol         and hexylene glycol. They may or may not be oxyethylenated (2 to         50 EO). Also exemplary are glycol ethers, such as ethoxydiglycol         or diethylene glycol monoethyl ether, marketed under the         trademark Transcutol HP by Gattefosse, propylene glycol laurate         marketed under the trademark Lauroglycol by Gattefosse,         propylene glycol dicaprate dicaprylate marketed under the         trademark Estol 1526 by Uniqema, and propylene glycol         dipelargonate.

The glycols that are preferred according to the invention are propylene glycol, dipropylene glycol, propylene glycol dipelargonate, propylene glycol laurate, ethoxydiglycol and propylene glycol dicaprate dicaprylate.

The pro-penetrating system also comprises at least one additional pro-penetrating agent.

The said additional pro-penetrating agent is selected from among the glycols listed above and the pro-penetrating agents of the family of fatty esters, fatty acids or fatty alcohols, or alcohols. Non-limiting examples of pro-penetrating agents according to the invention other than glycols are ethanol, dimethyl isosorbide marketed under the trademark Arlasolve DMI by Uniqema, methylpyrrolidone marketed under the trademark Pharmasolve by ISP, oleic acid marketed under the trademark Oléine V2 by Stéarinerie Dubois, PEG-8 capric/caprylic glycerides, marketed under the trademark Labrasol by Gattefosse, and oleyl alcohol marketed under the trademark HD Eutanol V PH by Cognis.

Preferably, the compositions according to the invention comprise the following combinations of pro-penetrating agents:

-   -   propylene glycol and dimethyl isosorbide,     -   propylene glycol and ethanol,     -   propylene glycol, diethylene glycol monoethyl ether and         propylene glycol laurate,     -   propylene glycol and methylpyrrolidone,     -   propylene glycol, dimethyl isosorbide and ethanol,     -   propylene glycol, methylpyrrolidone and oleyl alcohol.

Preferentially, the compositions according to the invention comprise from 20% to 60% by weight and preferably from 35% to 47% by weight of pro-penetrating glycol, relative to the total weight of the composition, and from 0.5% to 40% by weight and preferentially from 1% to 20% by weight of additional pro-penetrating agent, relative to the total weight of the composition.

The compositions according to the invention are emulsions and thus contain a fatty phase and an aqueous phase.

The fatty phase of the emulsions according to the invention may comprise fatty substances usually employed in the intended field of application.

Among these, exemplary are silicone fatty substances such as silicone oils, and also non-silicone fatty substances such as plant, mineral, animal or synthetic oils.

Among the silicone fatty substances, exemplary are:

-   -   (i) poly(C₁-C₂₀)alkylsiloxanes and especially those containing         trimethylsilyl endgroups, preferably those with a viscosity of         less than 0.06 m²/s, among which exemplary are linear         polydimethylsiloxanes and alkylmethylpolysiloxanes such as cetyl         dimethicone (CTFA name),     -   (ii) volatile silicone oils, such as:     -   cyclic volatile silicones having from 3 to 8 and preferably from         4 to 5 silicon atoms. They are preferably         cyclotetradimethylsiloxane, cyclopentadimethylsiloxane or         cyclohexadimethylsiloxane,     -   cyclocopolymers of the dimethylsiloxane/methylalkylsiloxane         type, such as Silicone FZ 3109 marketed by Union Carbide, which         is a dimethylsiloxane/methyloctylsiloxane cyclocopolymer,     -   linear volatile silicones having from 2 to 9 silicon atoms. They         are, for example, hexamethyldisiloxane,         hexylheptamethyltrisiloxane or octylheptamethyltrisiloxane,     -   (iii) phenylsilicone oils, especially those of formula:

in which:

-   -   R is a C1-C30 alkyl radical, an aryl radical or an aralkyl         radical,     -   n is an integer ranging from 0 and 100,     -   m is an integer ranging from 0 and 100, with the proviso that         the sum thereof ranges from 1 to 100.

Among the non-silicone fatty substances that are exemplary are common oils, such as liquid paraffin, liquid petroleum jelly, sweet almond oil, perhydrosqualene, apricot oil, wheatgerm oil, sweet almond oil, beauty-leaf oil, palm oil, castor oil, avocado oil, jojoba oil, olive oil or cereal germ oil; esters of fatty acids or of fatty alcohols, such as octyldodecyl alcohol or polyalcohol octanoates, decanoates or ricinoleates; fatty acid triglycerides; glycerides; hydrogenated polyisobutene, hydrogenated oils that are solid at 25° C.; lanolins; fatty esters that are solid at 25° C.

These fatty substances may be selected in particular in a varied manner by one skilled in this art in order to prepare a composition having the desired properties, for example in terms of consistency or texture.

Thus, the fatty phase of the emulsion according to the invention may be present in a content of from 5% to 50% by weight and preferably from 15% to 25% by weight relative to the total weight of the composition.

The aqueous phase of the emulsions according to the invention may comprise water, a floral water such as cornflower water, or a natural spring or mineral water selected, for example, from l'eau de Vittel, waters from the Vichy basin, l'eau d'Uriage, l'eau de la Roche Posay, l'eau de Bourboule, l'eau d'Enghien-les-Bains, l'eau de Saint Gervais-les-Bains, l'eau de Néris-les-Bains, l'eau d'Allevard-les-Bains, l'eau de Digne, l'eau de Maizières, l'eau de Neyrac-les-Bains, l'eau de Lons-le-Saunier, les Eaux Bonnes, l'eau de Rochefort, l'eau de Saint Christau, l'eau de Fumades, l'eau de Tercis-les-bains, l'eau d'Avène or l'eau d'Aix les Bains.

The said aqueous phase may be present in a content of from 10% to 70% by weight and preferably from 20% to 40% by weight relative to the total weight of the composition.

Advantageously, a stable emulsion according to the invention is obtained by preferably selecting at least one polymeric emulsifier as suitable emulsifying system.

Moreover, the emulsifying system is selected such that the compositions according to the invention are physically and chemically stable over time.

According to the invention, the term “physical stability” means a composition that does not present any macroscopic change of appearance (phase separation, change in color of appearance, etc.) or microscopic change of appearance (recrystallization of the active agent) after storage at temperatures of 25° C. (=room temperature: RT), 4° C. and 40° C., for 3 months.

According to the invention, the term “chemical stability” means a composition in which the content of active principle remains stable after three months at room temperature and at 40° C. A stable content of active principle means according to the invention that the content shows very little variation relative to the initial content, i.e., the variation in the content of active principle at time T should not be less than 90% to more particularly than 95% of the initial content at T0.

The difference from the polymeric emulsions and conventional emulsions is the manner in which the emulsion is created. Polymeric emulsions are stabilized by means of the formation of gel particles that surround the oil droplets. Thus, the oil droplet is immobilized in the gelled network and the emulsion is formed. Polymeric emulsions differ from standard emulsions stabilized with conventional emulsifying agents on account of their irritant potential: by virtue of their high molecular weight, polymeric emulsifiers are not capable of penetrating the stratum corneum.

Polymeric emulsifiers are especially described by Clymans & Brand in “Cosmetics and Toiletries” (provided worldwide, 1995, 119-125).

The most conventional polymeric emulsifiers are the Pemulen products obtained by grafting a linear carbon-based chain onto a synthetic polymer of vinyl or acrylic type that is initially totally hydrophilic. However, emulsions prepared with these polymeric emulsifiers have the drawback of being sensitive to electrolytes. Thus, in the present invention, the said crosslinked polymers of Pemulen type, and especially the products marketed by Goodrich under the trademarks Pemulen TR1, Pemulen TR2, Carbopol 1342 or Carbopol 1382, will not be used; these polymers, of acrylate/C10-30 alkyl acrylate crosspolymer type, which are copolymers comprising a major fraction of acrylic acid and a small fraction of C₁₀-C₃₀ (meth)acrylic acid esters, are thus excluded from the present invention.

On the other hand, as polymeric emulsifiers that may be employed according to the invention, and which do not have the drawbacks indicated above, exemplary are:

-   -   the Sepigel/Simulgel products, the Aristoflex products, which         are mixtures essentially comprising acrylic polymers combining         these acrylic polymers with a surfactant and/or a lipophilic         chain. They have colloidal, macromolecular surfactant and         emulsifying properties. Exemplary are Simulgel 600 (mixture of         polysorbate 80 and of isohexadecane and of acrylamide/sodium         acryloyldimethyltaurate) and the Sepiplus products marketed by         SEPPIC or the Aristoflex products (hydrophilic acrylic         polymers), and especially Aristoflex AVC (ammonium         acryloyldimethyltaurate/VP copolymer) or Aristoflex HMB marketed         by Clariant. Simulgel 600 and Aristoflex AVC will preferably be         employed according to the invention;     -   acrylic and cyanoacrylic polymers of Aculyn type, marketed by         Rohm & Haas, which are anionic associative rheology modifiers         and which act as polymeric emulsifiers. These polymers stabilize         the emulsion by trapping the oil drops in a three-dimensional         network of polymer chains, which avoids reagglomeration of the         oil drops and consequently stabilizes the emulsion. This type of         amphiphilic polymer combines hydrophilic and hydrophobic units,         which, in aqueous solution, become organized by forming         hydrophobic aggregates similar to surfactant miscelles. These         hydrophobic aggregates thus make it possible to formulate         emulsions that are very stable even without surfactant. Among         the emulsifiers that are preferred according to the invention,         Aculyn 22 (Acrylates/Steareth-20 Methacrylate Copolymer) will be         selected.

The compositions according to the invention comprise from 0.1% to 10% by weight, advantageously from 0.5% to 5% by weight and preferably from 0.2% to 3.5% by weight of suitable polymeric emulsifying system, relative to the total weight of the composition.

Moreover, depending on the nature of the emulsifier employed, the compositions according to the invention may comprise from 0 and 3% by weight and preferably from 0. 1% to 2% by weight, relative to the total weight of the composition, of at least one co-emulsifier, which, by reducing the surface tension of the dispersed phase, will allow adjustment of the droplets of the emulsion. The co-emulsifiers according to the invention may be selected from among esters of saturated or unsaturated, natural or synthetic fatty acids, especially of oleic acid or (iso)stearic acid, such as the polyglyceryl esters of isostearic acid marketed under the trademark Lameform TGI by Sidobre-Sinnova Henkel, sorbitan isostearate marketed under the trademark Arlacel 987 by Uniqema, sorbitan sesquioleate marketed under the trademark Arlacel 83 by Uniqema, sorbitan laurate marketed under the trademark Span 20 by Uniqema, esters of glycol and of isostearic acid, for instance PEG-6 isostearate marketed under the trademark Olepal Isostearique by Gattefosse, esters of sorbitol and of oleic acid, for instance the polysorbates marketed under the trademark Tween by Uniqema, fatty alcohol ethers, especially of oleyl alcohol, in particular esters of glycol and of oleyl alcohol, for instance the oleth products marketed under the trademark Brij by Uniqema, oxyethylenated sorbitan monostearate, and fatty alcohols such as stearyl alcohol or cetyl alcohol.

Sorbitan esters, especially sorbitan laurate, or polyglycerol esters will preferably be employed according to the invention.

Preferentially, the compositions according to the invention will comprise from 0.05% to 5% by weight and even more preferentially from 1% to 2% by weight of sorbitan esters or of polyglycerol esters, relative to the total weight of the composition.

Preferably, according to the invention, the composition comprises, formulated into a pharmaceutically acceptable vehicle:

-   -   0.0025% to 0.5% of clobetasol propionate,     -   30% to 50% of a pro-penetrating glycol,     -   1% to 20% of at least one additional pro-penetrating agent,     -   0.1% to 5% of at least one polymeric emulsifier,     -   0 to 5% of co-emulsifier.

Even more preferentially, the composition comprises:

-   -   0.0025% to 0.5% of clobetasol propionate,     -   30% to 50% of at least one pro-penetrating glycol selected from         among propylene glycol, diethylene glycol monoethyl ether and         propylene glycol laurate,     -   1% to 20% of at least one additional pro-penetrating agent         selected from among diethylene glycol monoethyl ether, propylene         glycol laurate, dimethyl isosorbide, ethanol and         methylpyrrolidone,     -   0.1% to 5% of at least one polymeric emulsifier selected from         among acrylic polymers and cyanoarylic polymers,     -   0 to 5% of co-emulsifier selected from among PEG-6 isostearate,         polyglyceryl-3 diisostearate and sorbitan laurate.

In one particular embodiment according to the invention, it has been found that it is possible to obtain a physically and chemically stable emulsion by employing an emulsifier alone without the presence of co-emulsifier or of gelling agent when the emulsifier is an emulsifier from the Sepigel/Simulgel family.

The pH of the compositions according to the invention advantageously ranges from 5 to 7.5 and preferably from 5.5 to 6.5. It will be adjusted to the desired value by adding common mineral or organic acids or bases.

The emulsions may also comprise any additive usually included in cosmetics or pharmaceuticals, such as gelling agents, antioxidants, dyes, fragrances, essential oils, preservatives, cosmetic active agents, moisturizers, vitamins, essential fatty acids, sphingolipids, self-tanning compounds such as DHA, sunscreens, liposoluble and especially hydrocarbon-based polymers, such as polybutene, polyalkylenes, polyacrylates and silicone polymers that are compatible with fatty substances. Needless to say, one skilled in this art will take care to select this or these optional additional compound(s), and/or the amount thereof, such that the advantageous properties of the composition according to the invention are not, or are not substantially, adversely affected by the envisaged addition.

These additives may be present in the composition in a proportion of from 0 to 10% by weight relative to the total weight of the composition.

The present invention also features administration of the subject compositions for the treatment of psoriasis, whether regime or regimen.

In order to further illustrate the present invention and the advantages thereof, the following specific examples are given, it being understood that same are intended only as illustrative and in nowise limitative. In said examples to follow, all parts and percentages are given by weight, unless otherwise indicated.

FORMULATION EXAMPLE 1

water qs 100 ammonium acryloyldimethyltaurate/VP copolymer 1.00% clobetasol propionate 0.05% propylene glycol 37.50% dimethyl isosorbide 10.00% liquid paraffin 20.00% PEG-6 isostearate 2.00% sodium hydroxide qs pH 6

Physical and chemical stability of the composition of Example 1:

T0 = thick white milk pH = 7.54 Centrifuge: 10,000 rpm: no comments T1 T2 T3 Micro: globule size <2.5 μm month months months RT Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, pH in accordance in accordance in accordance with T0 with T0 with T0 pH 7.6 pH 6.83 pH 6.85 Microscopic appearance Globule size 2.5 μm, Globule size 2.5 μm, Globule size 2.5 μm, homogeneous homogeneous homogeneous carpet carpet carpet Assay of the active agent 97.9% 98.5% 98.5% (HPLC) T0: 99% Macroscopic appearance Thick white miik, Thick white milk, Thick white milk, in accordance in accordance in accordance with T0 with T0 with T0  4° C. Microscopic appearance Globule size 2.5 μm, Globule size 2.5 μm, Globule size 2.5 μm, homogeneous homogeneous homogeneous carpet carpet carpet No No No recrystallization recrystallization recrystallization of the clobetasol of the clobetasol of the clobetasol Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, in accordance in accordance in accordance with T0 with T0 with T0 40° C. Assay of the active agent 96.3% 97% 95.7% (HPLC) T0: 99%

FORMULATION EXAMPLE 2

water qs 100 ammonium acryloyldimethyltaurate/VP copolymer 1.00% clobetasol propionate 0.05% propylene glycol 42.50% ethanol 5.00% liquid paraffin 20.00% PEG-6 isostearate 2.00% sodium hydroxide qs pH 6

T0 = thick white milk pH = 6.7 Centrifuge: 10,000 rpm: no comments T1 T2 T3 Micro: globule size <2.5 μm month months months RT Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, pH in accordance in accordance in accordance with T0 with T0 with T0 pH 6.7 pH 6.35 pH 6.51 Microscopic appearance Globule size from Globule size from Globule size from 2.5 μm and 7.5 μm, 2.5 μm and 7.5 μm, 2.5 μm and 7.5 μm, Assay of the active agent 98.1% 98.5% 99.1% (HPLC) T0: 99.7%  4° C. Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, in accordance in accordance in accordance with T0 with T0 with T0 Microscopic appearance Globule size from Globule size from Globule size from 2.5 μm and 7.5 μm, 2.5 μm and 7.5 μm, 2.5 μm and 7.5 μm, heterogeneous heterogeneous heterogeneous carpet carpet carpet No No No recrystallization recrystallization recrystallization of the clobetasol of the clobetasol of the clobetasol 40° C. Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, in accordance in accordance in accordance with T0 with T0 with T0 Assay of the active agent 97.4% 96.9% 96.8% (HPLC) T0: 99.7%

FORMULATION EXAMPLE 3

water qs 100 acrylates/steareth-20 methacrylate copolymer 3.50% clobetasol propionate 0.05% propylene glycol 45.00% diethylene glycol monoethyl ether 1.50% propylene glycol laurate 1.00% liquid paraffin 20.00% polyglyceryl-3 diisostearate 2.00% sodium hydroxide qs pH 6

T0 = Liquid white milk pH = 6.33 Centrifuge: 10,000 rpm: slight phase separation T1 T2 T3 Micro: globule size <2.5 μm month months months RT Macroscopic appearance Liquid white milk, Liquid white milk, Liquid white milk, pH in accordance in accordance with in accordance with T0 T0 with T0 pH 6.36 pH 6.29 pH 6.35 Microscopic appearance Globule size <2.5 μm, Globule size <2.5 μm, Globule size <2.5 μm, homogeneous homogeneous homogeneous carpet carpet carpet Assay of the active 98.3% 99.9% 98.1% agent (HPLC) T0: 99.6%  4° C. Macroscopic appearance Liquid white milk, Liquid white milk, Liquid white milk, in accordance in accordance with in accordance with T0 T0 with T0 Microscopic appearance Globule size <2.5 μm, Globule size <2.5 μm, Globule size <2.5 μm, homogeneous homogeneous homogeneous carpet carpet carpet No No No recrystallization recrystallization of recrystallization of the clobetasol the clobetasol of the clobetasol 40° C. Macroscopic appearance Liquid white milk, Liquid white milk, Liquid white milk, in accordance in accordance with in accordance with T0 T0 with T0 Assay of the active 97.6% 99% 96.5% agent (HPLC) T0: 99.6%

FORMULATION EXAMPLE 4

water qs 100 acrylamide/sodium acryloyldimethyltaurate (and) isohexadecane 2.00% (and) polysorbate 80 clobetasol propionate 0.05% propylene glycol 46.50% methylpyrrolidone 1.00% liquid paraffin 20.00%

T0 = thick white milk pH = 6.51 Centrifuge: 10 000 rpm: no comments Micro: globule size 2.5 to T1 T2 T3 7.5 μm month months months RT Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, pH in accordance in accordance in accordance with T0 with T0 with T0 pH 6.47 pH 6.45 pH 6.08 Microscopic appearance Globule size 7.5 μm Globule size 7.5 μm Globule size to 15 μm to 15 μm 7.5 μm to 25 μm Assay of the active 97.4% 102.6% 94.8% agent (HPLC) T0: 101.1%  4° C. Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, in accordance in accordance in accordance with T0 with T0 with T0 Microscopic appearance Globule size 7.5 μm Globule size 7.5 μm Globule size to 15 μm to 15 μm 7.5 μm to 25 μm No No No recrystallization recrystallization recrystallization of the clobetasol of the clobetasol of the clobetasol 40° C. Macroscopic appearance Thick white milk, Thick white milk, Thick white milk, in accordance in accordance in accordance with T0 with T0 with T0 Assay of the active 97.5% 98.4% 90.4% agent (HPLC) T0: 101.1%

Each patent, patent application, publication, text and literature article/report cited or indicated herein is hereby expressly incorporated by reference in its entirety.

While the invention has been described in terms of various specific and preferred embodiments, the skilled artisan will appreciate that various modifications, substitutions, omissions, and changes may be made without departing from the spirit thereof. Accordingly, it is intended that the scope of the present invention be limited solely by the scope of the following claims, including equivalents thereof. 

What is claimed is:
 1. A topically applicable, pharmaceutical composition comprising a physically and chemically stable oil-in-water emulsion which comprises: (a) 0.0025% to 0.5% of clobetasol propionate, said clobetasol propionate being the only active ingredient in the composition; (b) a pro-penetrating system which consists of 30% to 50% of at least one glycol selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, pentylene glycol, hexylene glycol, propylene glycol dipelargonate, diethylene glycol monoethyl ether, propylene glycol laurate, propylene glycol dicaprate dicaprylate and ethoxydiglycol; and 1% to 20% of at least one additional pro-penetrating agent selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, pentylene glycol, hexylene glycol, propylene glycol dipelargonate, diethylene glycol monoethyl ether, propylene glycol laurate, propylene glycol dicaprate dicaprylate, ethoxydiglycol, ethanol, dimethyl isosorbide, methylpyrrolidone, oleic acid, PEG-8 capric/caprylic glycerides and oleyl alcohol; said pro-penetrating system being the only pro-penetrating system in the composition; (c) an emulsifier which consists of 0.1% to 5% of at least one polymeric emulsifier which is selected from the group consisting of ammonium acryloyldimethyltaurate/VP copolymer and acrylates/steareth-20 methacrylate copolymer, said emulsifier being the only emulsifier(s) in the composition; (d) an oil, (e) water, and (f) optionally, sodium hydroxide, for adjusting the pH of the emulsion to from 5 to 7.5; said composition being devoid of any copolymer comprising a major fraction of acrylic acid and a minor fraction of C₁₀-C₃₀ (meth) acrylic acid esters, wherein all percents are by weight with respect to the total weight of the composition.
 2. The pharmaceutical composition as defined by claim 1, said pro-penetrating system consisting of: (a) propylene glycol and dimethyl isosorbide, (b) propylene glycol and ethanol, (c) propylene glycol, diethylene glycol monoethyl ether and propylene glycol laurate, (d) propylene glycol and methylpyrrolidone, (e) propylene glycol, dimethyl isosorbide and ethanol, or (f) propylene glycol, methylpyrrolidone and oleyl alcohol.
 3. A topically applicable, pharmaceutical composition comprising a physically and chemically stable oil-in-water emulsion which consists of: (a) 0.0025% to 0.5% of clobetasol propionate, said clobetasol propionate being the only active ingredient in the composition; (b) a pro-penetrating system which consists of 30% to 50% of at least one glycol selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, pentylene glycol, hexylene glycol, propylene glycol dipelargonate, diethylene glycol monoethyl ether, propylene glycol laurate, propylene glycol dicaprate dicaprylate and ethoxydiglycol; and 1% to 20% of at least one additional pro-penetrating agent selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, dipropylene butylene glycol, pentylene glycol, hexylene glycol, propylene glycol dipelargonate, diethylene glycol monoethyl ether, propylene glycol laurate, propylene glycol dicaprate dicaprylate, ethoxydiglycol, ethanol, dimethyl isosorbide, methylpyrrolidone, oleic acid, PEG-8 capric/caprylic glycerides and oleyl alcohol; said pro-penetrating system being the only pre-penetrating system in the composition; (c) an emulsifier which consists of 0.1% to 5% of at least one polymeric emulsifier which is selected from the group consisting of ammonium acryloyldimethyltaurateNP copolymer and acrylates/steareth-20 methacrylate copolymer; (d) an oil, (e) water, (f) optionally, sodium hydroxide, for adjusting the pH of the emulsion to from 5 to 7.5; and (g) up to 5% of at least one co-emulsifier selected from the group consisting of polyglycerol esters of isostearic acid, sorbitan isostearate, sorbitan sesquioleate, sorbitan laurate, glycol esters of isostearic acid, sorbitol esters of oleic acid, glycol esters of oleyl alcohol, oxyethylenated sorbitan monostearate, stearyl alcohol and cetyl alcohol; said emulsifier (c) and said co-emulsifier (g) being the only emulsifier(s)/co-emulsifier(s) in the composition; said composition being devoid of any copolymer comprising a major fraction of acrylic acid and a minor fraction of C₁₀-C₃₀ (meth) acrylic acid esters, wherein all percents are by weight with respect to the total weight of the composition.
 4. The pharmaceutical composition as defined by claim 3, wherein: the at least one glycol is selected from the group consisting of propylene glycol, diethylene glycol monoethyl ether and propylene glycol laurate, the at least one additional pro-penetrating agent is selected from the group consisting of diethylene glycol monoethyl ether, propylene glycol laurate, dimethyl isosorbide, ethanol and methylpyrrolidone, and the at least one co-emulsifier is selected from the group consisting of PEG-6 isostearate, sorbitan laurate and polyglyceryl-3 diisostearate.
 5. A regime or regimen for the treatment of psoriasis, comprising topically applying onto the affected skin area of an individual afflicted therewith, a thus effective amount of the pharmaceutical composition as defined by claim
 1. 6. The pharmaceutical composition as defined by claim 1, wherein the at least one glycol is present in the composition at from 35% to 47% by weight.
 7. The pharmaceutical composition as defined by claim 3, wherein the propenetrating system consists of propylene glycol and dimethylisosorbide, the emulsifier consists of ammonium acryloyldimethyltaurate/VP copolymer, the co-emulsifier consists of PEG-6 isostearate, and the oil consists of liquid paraffin.
 8. The pharmaceutical composition as defined by claim 3, wherein the propenetrating system consists of propylene glycol and ethanol, the emulsifier consists of ammonium acryloyldimethyltaurate/VP copolymer, the co-emulsifier consists of PEG-6 isostearate, and the oil consists of liquid paraffin.
 9. The pharmaceutical composition as defined by claim 3, wherein the propenetrating system consists of propylene glycol, diethylene glycol monoethyl ether and propylene glycol laurate, the emulsifier consists of acrylates/steareth-20 methacrylate copolymer, the co-emulsifier consists of polyglyceryl-3 diisostearate, and the oil consists of liquid paraffin. 